Lacrimal bone

The lacrimal bone (Latin: os lacrimale) is the smallest and the thinnest bone of the skull. It is a paired bone that lies anteriorly in the medial wall of each orbit. Each lacrimal bone has two surfaces (lateral and medial) and four borders (anterior, posterior, superior, and inferior).

The lateral surface of the lacrimal bone, also known as the orbital surface, is divided by a vertically oriented bony projection called the posterior lacrimal crest. Anterior to the posterior lacrimal crest lies a vertical groove known as the lacrimal groove.

The lacrimal groove is a groove for the nasolacrimal duct in the anterior part of the lateral surface of the lacrimal bone, and it continues on the frontal process of the maxilla. The medial wall of the groove has a descending extension that contributes to the formation of the nasolacrimal canal. The lacrimal groove of the lacrimal bone fuses anteriorly with the posterior border of the frontal process of the maxilla to form a fossa that houses the lacrimal sac.

The medial surface of the lacrimal bone, also called the nasal surface, presents a longitudinal ridge corresponding to the lacrimal crest on the lateral surface. The anterior region of the lacrimal bone's medial surface forms a part of the middle nasal meatus.

The anterior border of the lacrimal bone articulates with the frontal process of the maxilla. The posterior border connects with the orbital plate of the ethmoid bone. The superior border articulates with the frontal bone. And the inferior border of the lacrimal bone articulates with the orbital surface of the maxilla. The anterior portion of the inferior border is prolonged downward and articulates with the lacrimal process of the inferior nasal concha, contributing to the formation of the nasolacrimal canal.